Pump cannot build adequate pressure

I have a 1HP submersible at 40 feet in a 80 foot well. The well is 6-7 years old. I just had the two 20' galvanized pipes in the well replaced last year as a result of a leak, when the pump stayed on with low pressure. This leads me to believe it is a different problem than last years leaking galvanized well pipe, but it I suppose they could have gone bad again after only a year.

The pump stays on and will not go above 20#'s of pressure. I have a 120 gallon holding tank that my pressure switch and gauge are attached to. It didn't appear to be waterlogged, but just in case I drained that tank and took out the plug in the top of the tank to make sure air got back in it. I screwed the plug back in the tank and turned the pump back on, but again pressure only hit 20#s. My normal setting is 50# min and 70# max.

Do you have any suggestions on how to isolate the problem? Mainly I wanted to make sure it wasn't something simple before calling the well guy which has been running me about $500 almost once a year. Between corroded wires, lightning strikes, and leaking pipes I have had to have my pump pulled out the ground 4 times in the past six years.

If I need a new pump I would like to increase capacity from 1HP to maybe 1.5HP. Is that advisable, and what is the best submersible pump?